Combined Neurophysiologic and Neuroimaging Approach to Reveal the Structure-Function Paradox in Cervical Myelopathy

Neurology ◽  
2021 ◽  
pp. 10.1212/WNL.0000000000012643
Author(s):  
Paulina Simonne Scheuren ◽  
Gergely David ◽  
John Lawrence Kipling Kramer ◽  
Catherine Ruth Jutzeler ◽  
Markus Hupp ◽  
...  
Keyword(s):  
Evoked Potentials ◽  
Structure Function ◽  
Cervical Myelopathy ◽  
Structural Damage ◽  
Quantitative Sensory Testing ◽  
Sensory Testing ◽  
Contact Heat ◽  
Spinothalamic Tract ◽  
Functional Integrity ◽  
Nociceptive Pathways

Objective:To explore the so-called “structure-function paradox” in individuals with focal spinal lesions by means of tract-specific MRI coupled with multi-modal evoked potentials and quantitative sensory testing.Methods:Individuals with signs and symptoms attributable to cervical myelopathy (i.e., no evidence of competing neurological diagnosis) were recruited in the Balgrist University Hospital, Zurich, Switzerland between February 2018 and March 2019. We evaluated the relationship between the extent of structural damage within spinal nociceptive pathways (i.e., dorsal horn, spinothalamic tract, anterior commissure) assessed with atlas-based MRI , and 1) the functional integrity of spinal nociceptive pathways measured with contact heat-, cold-, and pinprick- evoked potentials and 2) clinical somatosensory phenotypes assessed with quantitative sensory testing.Results:Sixteen individuals (mean age 61 years) with either degenerative (N=13) or post-traumatic (N=3) cervical myelopathy participated in the study. Most individuals presented with mild myelopathy (modified Japanese Orthopaedic Association score (mJOA)>15; N=13). 71% of individuals presented with structural damage within spinal nociceptive pathways on MRI. Yet, 50% of these individuals presented with complete functional sparing (i.e., normal contact heat-, cold-, and pinprick- evoked potentials). The extent of structural damage within spinal nociceptive pathways was neither associated with functional integrity of thermal (heat: p=0.57; cold: p=0.49) and mechano-nociceptive pathways (p=0.83) nor with the clinical somatosensory phenotype (heat: p=0.16; cold: p=0.37; mechanical: p=0.73). The amount of structural damage to the spinothalamic tract did not correlate with spinothalamic conduction velocity (p>0.05; rho=-0.11).Conclusions:Our findings provide neurophysiological evidence to substantiate that structural damage in the spinal cord does not equate to functional somatosensory deficits. This study recognizes the pronounced structure-function paradox in cervical myelopathies and underlines the inevitable need for a multi-modal phenotyping approach to reveal the eloquence of lesions within somatosensory pathways.

Development of a novel brief quantitative sensory testing protocol that integrates static and dynamic pain assessments: Test-retest performance in healthy adults

Pain Medicine ◽  
2021 ◽  
Author(s):  
Martin J De Vita ◽  
Katherine Buckheit ◽  
Christina E Gilmour ◽  
Dezarie Moskal ◽  
Stephen A Maisto
Keyword(s):  
Quantitative Sensory Testing ◽  
Temporal Summation ◽  
Pain Threshold ◽  
Pain Modulation ◽  
Healthy Adults ◽  
Dynamic Responses ◽  
Conditioned Pain Modulation ◽  
Sensory Testing ◽  
Contact Heat ◽  
Intraclass Correlations

Abstract Objective Quantitative sensory testing is an expanding pain research domain with numerous clinical and research applications. There is a recognized need for brief reliable quantitative sensory testing protocols that enhance assessment feasibility. This study aimed to integrate static (pain threshold, tolerance, suprathreshold) and dynamic (conditioned pain modulation, offset analgesia, temporal summation) pain reactivity measures into a brief 20-minute protocol that uses a single portable device. The test-retest performance of this optimized protocol was evaluated. Design Using a test-retest design, the brief quantitative sensory testing assessment was administered to participants on two occasions separated by exactly 7 days. Setting A clinical psychology research laboratory at Syracuse University. Subjects Participants were 33 healthy adults recruited from Syracuse University’s online research participation pool. Methods A portable computerized quantitative sensory testing device delivered contact-heat pain to assess static and dynamic pain measures in participants. Dynamic responses were continuously recorded using a computerized visual analog scale. Results Pain threshold, tolerance, and suprathreshold exhibited excellent reliability (intraclass correlations ranged from 0.80 to 0.83). Conditioned pain modulation, offset analgesia, temporal summation yielded reliability in the good to excellent range (intraclass correlations ranged from 0.66 to 0.71). Conclusions Findings suggested that this brief integrated QST protocol may reliably monitor human pain reactivity over brief periods. This protocol may enhance quantitative sensory testing feasibility in clinical and research settings.

Assessment of small fibers using evoked potentials

2014 ◽  
Vol 5 (2) ◽  
pp. 111-118 ◽  
Author(s):  
Caspar Skau Madsen ◽  
Nanna Brix Finnerup ◽  
Ulf Baumgärtner
Keyword(s):  
Neuropathic Pain ◽  
Evoked Potentials ◽  
Type I ◽  
Contact Heat ◽  
Brain Potentials ◽  
Pain Mechanisms ◽  
Future Studies ◽  
Nociceptive Pathways ◽  
Small Fiber ◽  
Related Potentials

AbstractBackground and purposeConventional neurophysiological techniques do not assess the function of nociceptive pathways and are inadequate to detect abnormalities in patients with small-fiber damage. This overview aims to give an update on the methods and techniques used to assess small fiber (Aδ- and C-fibers) function using evoked potentials in research and clinical settings.MethodsNoxious radiant or contact heat allows the recording of heat-evoked brain potentials commonly referred to as laser evoked potentials (LEPs) and contact heat-evoked potentials (CHEPs). Both methods reliably assess the loss of Aδ-fiber function by means of reduced amplitude and increased latency of late responses, whereas other methods have been developed to record ultra-late C-fiber-related potentials. Methodological considerations with the use of LEPs and CHEPs include fixed versus variable stimulation site, application pressure, and attentional factors. While the amplitude of LEPs and CHEPs often correlates with the reported intensity of the stimulation, these factors may also be dissociated. It is suggested that the magnitude of the response may be related to the saliency of the noxious stimulus (the ability of the stimulus to stand out from the background) rather than the pain perception.ResultsLEPs and CHEPs are increasingly used as objective laboratory tests to assess the pathways mediating thermal pain, but new methods have recently been developed to evaluate other small-fiber pathways. Pain-related electrically evoked potentials with a low-intensity electrical simulation have been proposed as an alternative method to selectively activate Aδ-nociceptors. A new technique using a flat tip mechanical stimulator has been shown to elicit brain potentials following activation of Type I A mechano-heat (AMH) fibers. These pinprick-evoked potentials (PEP) have a morphology resembling those of heat-evoked potentials following activation of Type II AMH fibers, but with a shorter latency. Cool-evoked potentials can be used for recording the non-nociceptive pathways for cooling. At present, the use of cool-evoked potentials is still in the experimental state. Contact thermodes designed to generate steep heat ramps may be programmed differently to generate cool ramps from a baseline of 35◦C down to 32◦C or 30◦C. Small-fiber evoked potentials are valuable tools for assessment of small-fiber function in sensory neuropathy, central nervous system lesion, and for the diagnosis of neuropathic pain. Recent studies suggest that both CHEPs and pinprick-evoked potentials may also be convenient tools to assess sensitization of the nociceptive system.ConclusionsIn future studies, small-fiber evoked potentials may also be used in studies that aim to understand pain mechanisms including different neuropathic pain phenotypes, such as cold- or touch-evoked allodynia, and to identify predictors of response to pharmacological pain treatment.ImplicationsFuture studies are needed for some of the newly developed methods.

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